Machines for heating articles or products by condensing vapors on them are known (see for example FR-A-2.243.045, FR-A-2.553.186 and U.S. Pat. No. 4,055,217). In these machines the articles or products are heated to the desired temperature by the condensation of a primary vapor. As the primary liquid constituting the source of the primary vapor is usually a very expensive inert, high boiling point perfluorocarbon liquid, it is customary to confine the primary vapor mass in relation to the atmosphere by means of a secondary vapor mass generated from a secondary liquid, usually a chlorofluorocarbon, having a lower boiling point than the primary liquid. It is also known to provide means for condensing the secondary vapor, in order to prevent it from escaping to the atmosphere, and for recycling the primary vapor condensate to the machine. It is also known to separate the secondary liquid from the water originating from the atmosphere and contained in the condensate by eliminating the supernatant water in a separator (see for example U.S. Pat. No. 3,632,480 and EP-A-0112.484).